1 /*
2 * Copyright (c) 2000, 2006, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.awt.image;
27
28 import java.awt.Color;
29 import java.awt.Graphics;
30 import java.awt.Graphics2D;
31 import java.awt.GraphicsConfiguration;
32 import java.awt.GraphicsDevice;
33 import java.awt.Image;
34 import java.awt.ImageCapabilities;
35 import java.awt.Toolkit;
36 import java.awt.Transparency;
37
38 /**
39 * VolatileImage is an image which can lose its
40 * contents at any time due to circumstances beyond the control of the
41 * application (e.g., situations caused by the operating system or by
42 * other applications). Because of the potential for hardware acceleration,
43 * a VolatileImage object can have significant performance benefits on
44 * some platforms.
45 * <p>
46 * The drawing surface of an image (the memory where the image contents
47 * actually reside) can be lost or invalidated, causing the contents of that
48 * memory to go away. The drawing surface thus needs to be restored
49 * or recreated and the contents of that surface need to be
50 * re-rendered. VolatileImage provides an interface for
51 * allowing the user to detect these problems and fix them
52 * when they occur.
53 * <p>
54 * When a VolatileImage object is created, limited system resources
55 * such as video memory (VRAM) may be allocated in order to support
56 * the image.
57 * When a VolatileImage object is no longer used, it may be
58 * garbage-collected and those system resources will be returned,
59 * but this process does not happen at guaranteed times.
60 * Applications that create many VolatileImage objects (for example,
61 * a resizing window may force recreation of its back buffer as the
62 * size changes) may run out of optimal system resources for new
63 * VolatileImage objects simply because the old objects have not
64 * yet been removed from the system.
65 * (New VolatileImage objects may still be created, but they
66 * may not perform as well as those created in accelerated
67 * memory).
68 * The flush method may be called at any time to proactively release
69 * the resources used by a VolatileImage so that it does not prevent
70 * subsequent VolatileImage objects from being accelerated.
71 * In this way, applications can have more control over the state
72 * of the resources taken up by obsolete VolatileImage objects.
73 * <p>
74 * This image should not be subclassed directly but should be created
75 * by using the {@link java.awt.Component#createVolatileImage(int, int)
76 * Component.createVolatileImage} or
77 * {@link java.awt.GraphicsConfiguration#createCompatibleVolatileImage(int, int)
78 * GraphicsConfiguration.createCompatibleVolatileImage(int, int)} methods.
79 * <P>
80 * An example of using a VolatileImage object follows:
81 * <pre>
82 * // image creation
83 * VolatileImage vImg = createVolatileImage(w, h);
84 *
85 *
86 * // rendering to the image
87 * void renderOffscreen() {
88 * do {
89 * if (vImg.validate(getGraphicsConfiguration()) ==
90 * VolatileImage.IMAGE_INCOMPATIBLE)
91 * {
92 * // old vImg doesn't work with new GraphicsConfig; re-create it
93 * vImg = createVolatileImage(w, h);
94 * }
95 * Graphics2D g = vImg.createGraphics();
96 * //
97 * // miscellaneous rendering commands...
98 * //
99 * g.dispose();
100 * } while (vImg.contentsLost());
101 * }
102 *
103 *
104 * // copying from the image (here, gScreen is the Graphics
105 * // object for the onscreen window)
106 * do {
107 * int returnCode = vImg.validate(getGraphicsConfiguration());
108 * if (returnCode == VolatileImage.IMAGE_RESTORED) {
109 * // Contents need to be restored
110 * renderOffscreen(); // restore contents
111 * } else if (returnCode == VolatileImage.IMAGE_INCOMPATIBLE) {
112 * // old vImg doesn't work with new GraphicsConfig; re-create it
113 * vImg = createVolatileImage(w, h);
114 * renderOffscreen();
115 * }
116 * gScreen.drawImage(vImg, 0, 0, this);
117 * } while (vImg.contentsLost());
118 * </pre>
119 * <P>
120 * Note that this class subclasses from the {@link Image} class, which
121 * includes methods that take an {@link ImageObserver} parameter for
122 * asynchronous notifications as information is received from
123 * a potential {@link ImageProducer}. Since this {@code VolatileImage}
124 * is not loaded from an asynchronous source, the various methods that take
125 * an {@code ImageObserver} parameter will behave as if the data has
126 * already been obtained from the {@code ImageProducer}.
127 * Specifically, this means that the return values from such methods
128 * will never indicate that the information is not yet available and
129 * the {@code ImageObserver} used in such methods will never
130 * need to be recorded for an asynchronous callback notification.
131 * @since 1.4
132 */
133 public abstract class VolatileImage extends Image implements Transparency
134 {
135
136 // Return codes for validate() method
137
138 /**
139 * Validated image is ready to use as-is.
140 */
141 public static final int IMAGE_OK = 0;
142
143 /**
144 * Validated image has been restored and is now ready to use.
145 * Note that restoration causes contents of the image to be lost.
146 */
147 public static final int IMAGE_RESTORED = 1;
148
149 /**
150 * Validated image is incompatible with supplied
151 * {@code GraphicsConfiguration} object and should be
152 * re-created as appropriate. Usage of the image as-is
153 * after receiving this return code from {@code validate}
154 * is undefined.
155 */
156 public static final int IMAGE_INCOMPATIBLE = 2;
157
158 /**
159 * Returns a static snapshot image of this object. The
160 * {@code BufferedImage} returned is only current with
161 * the {@code VolatileImage} at the time of the request
162 * and will not be updated with any future changes to the
163 * {@code VolatileImage}.
164 * @return a {@link BufferedImage} representation of this
165 * {@code VolatileImage}
166 * @see BufferedImage
167 */
168 public abstract BufferedImage getSnapshot();
169
170 /**
171 * Returns the width of the {@code VolatileImage}.
172 * @return the width of this {@code VolatileImage}.
173 */
174 public abstract int getWidth();
175
176 /**
177 * Returns the height of the {@code VolatileImage}.
178 * @return the height of this {@code VolatileImage}.
179 */
180 public abstract int getHeight();
181
182 // Image overrides
183
184 /**
185 * This returns an ImageProducer for this VolatileImage.
186 * Note that the VolatileImage object is optimized for
187 * rendering operations and blitting to the screen or other
188 * VolatileImage objects, as opposed to reading back the
189 * pixels of the image. Therefore, operations such as
190 * {@code getSource} may not perform as fast as
191 * operations that do not rely on reading the pixels.
192 * Note also that the pixel values read from the image are current
193 * with those in the image only at the time that they are
194 * retrieved. This method takes a snapshot
195 * of the image at the time the request is made and the
196 * ImageProducer object returned works with
197 * that static snapshot image, not the original VolatileImage.
198 * Calling getSource()
199 * is equivalent to calling getSnapshot().getSource().
200 * @return an {@link ImageProducer} that can be used to produce the
201 * pixels for a {@code BufferedImage} representation of
202 * this Image.
203 * @see ImageProducer
204 * @see #getSnapshot()
205 */
206 public ImageProducer getSource() {
207 // REMIND: Make sure this functionality is in line with the
208 // spec. In particular, we are returning the Source for a
209 // static image (the snapshot), not a changing image (the
210 // VolatileImage). So if the user expects the Source to be
211 // up-to-date with the current contents of the VolatileImage,
212 // they will be disappointed...
213 // REMIND: This assumes that getSnapshot() returns something
214 // valid and not the default null object returned by this class
215 // (so it assumes that the actual VolatileImage object is
216 // subclassed off something that does the right thing
217 // (e.g., SunVolatileImage).
218 return getSnapshot().getSource();
219 }
220
221 // REMIND: if we want any decent performance for getScaledInstance(),
222 // we should override the Image implementation of it...
223
224 /**
225 * This method returns a {@link Graphics2D}, but is here
226 * for backwards compatibility. {@link #createGraphics() createGraphics} is more
227 * convenient, since it is declared to return a
228 * {@code Graphics2D}.
229 * @return a {@code Graphics2D}, which can be used to draw into
230 * this image.
231 */
232 public Graphics getGraphics() {
233 return createGraphics();
234 }
235
236 /**
237 * Creates a {@code Graphics2D}, which can be used to draw into
238 * this {@code VolatileImage}.
239 * @return a {@code Graphics2D}, used for drawing into this
240 * image.
241 */
242 public abstract Graphics2D createGraphics();
243
244
245 // Volatile management methods
246
247 /**
248 * Attempts to restore the drawing surface of the image if the surface
249 * had been lost since the last {@code validate} call. Also
250 * validates this image against the given GraphicsConfiguration
251 * parameter to see whether operations from this image to the
252 * GraphicsConfiguration are compatible. An example of an
253 * incompatible combination might be a situation where a VolatileImage
254 * object was created on one graphics device and then was used
255 * to render to a different graphics device. Since VolatileImage
256 * objects tend to be very device-specific, this operation might
257 * not work as intended, so the return code from this validate
258 * call would note that incompatibility. A null or incorrect
259 * value for gc may cause incorrect values to be returned from
260 * {@code validate} and may cause later problems with rendering.
261 *
262 * @param gc a {@code GraphicsConfiguration} object for this
263 * image to be validated against. A null gc implies that the
264 * validate method should skip the compatibility test.
265 * @return {@code IMAGE_OK} if the image did not need validation<BR>
266 * {@code IMAGE_RESTORED} if the image needed restoration.
267 * Restoration implies that the contents of the image may have
268 * been affected and the image may need to be re-rendered.<BR>
269 * {@code IMAGE_INCOMPATIBLE} if the image is incompatible
270 * with the {@code GraphicsConfiguration} object passed
271 * into the {@code validate} method. Incompatibility
272 * implies that the image may need to be recreated with a
273 * new {@code Component} or
274 * {@code GraphicsConfiguration} in order to get an image
275 * that can be used successfully with this
276 * {@code GraphicsConfiguration}.
277 * An incompatible image is not checked for whether restoration
278 * was necessary, so the state of the image is unchanged
279 * after a return value of {@code IMAGE_INCOMPATIBLE}
280 * and this return value implies nothing about whether the
281 * image needs to be restored.
282 * @see java.awt.GraphicsConfiguration
283 * @see java.awt.Component
284 * @see #IMAGE_OK
285 * @see #IMAGE_RESTORED
286 * @see #IMAGE_INCOMPATIBLE
287 */
288 public abstract int validate(GraphicsConfiguration gc);
289
290 /**
291 * Returns {@code true} if rendering data was lost since last
292 * {@code validate} call. This method should be called by the
293 * application at the end of any series of rendering operations to
294 * or from the image to see whether
295 * the image needs to be validated and the rendering redone.
296 * @return {@code true} if the drawing surface needs to be restored;
297 * {@code false} otherwise.
298 */
299 public abstract boolean contentsLost();
300
301 /**
302 * Returns an ImageCapabilities object which can be
303 * inquired as to the specific capabilities of this
304 * VolatileImage. This would allow programmers to find
305 * out more runtime information on the specific VolatileImage
306 * object that they have created. For example, the user
307 * might create a VolatileImage but the system may have
308 * no video memory left for creating an image of that
309 * size, so although the object is a VolatileImage, it is
310 * not as accelerated as other VolatileImage objects on
311 * this platform might be. The user might want that
312 * information to find other solutions to their problem.
313 * @return an {@code ImageCapabilities} object that contains
314 * the capabilities of this {@code VolatileImage}.
315 * @since 1.4
316 */
317 public abstract ImageCapabilities getCapabilities();
318
319 /**
320 * The transparency value with which this image was created.
321 * @see java.awt.GraphicsConfiguration#createCompatibleVolatileImage(int,
322 * int,int)
323 * @see java.awt.GraphicsConfiguration#createCompatibleVolatileImage(int,
324 * int,ImageCapabilities,int)
325 * @see Transparency
326 * @since 1.5
327 */
328 protected int transparency = TRANSLUCENT;
329
330 /**
331 * Returns the transparency. Returns either OPAQUE, BITMASK,
332 * or TRANSLUCENT.
333 * @return the transparency of this {@code VolatileImage}.
334 * @see Transparency#OPAQUE
335 * @see Transparency#BITMASK
336 * @see Transparency#TRANSLUCENT
337 * @since 1.5
338 */
339 public int getTransparency() {
340 return transparency;
341 }
342 }